The present invention relates to equipment for bending and pressing wood laminations into curved forms.
Curved wood forms have long been used in a variety of applications. Curves desired include cyma curves, arcs, circles, S-curves and other shapes. Production of wood members having a desired curved form has previously been achieved by utilizing wood which grew in that form, by cutting the form from stock large enough to accommodate the curve, by steam-bending techniques, and by glue laminating thin layers of wood which can easily be bent into the desired form prior to bonding the laminations together. Curved members formed of laminations are highly desirable in many applications because of the superior strength and stability of such members as compared to solid wood structures of the same size and shape, because very tight curves can be achieved and because curved shapes can be produced which are not possible using solid wood.
Production of large-scale, multi-lamination wood forms is difficult, however, because of the need for a means for bending the laminations to and holding them in precisely the correct shape and relationship for a sufficient period of time to permit the adhesive or glue being used to cure. This must normally be accomplished by applying substantial amounts of opposing pressure normal to and distributed over substantially all of both sides of a workpiece made up of multiple layers of wood and uncured adhesive or glue.
A variety of shop-built and commercial machinery has previously been used to fabricate such curved members, including the Casati Macchine ARC50 arch bending machine available from Casati Macchine at 20027 Rescaldina (MI), Italy; the Stegherr RP and RSP bending and laminating fixtures available from Stegherr Maschinenbau GmbH and Co. K.G., Donaustaufer Strabe 30-Postbox 120449, D-8400 Regensburg 12, West Germany; and the devices disclosed in U.S. Pat. Nos. 927,975, 1,561,613, 2,331,972, 2,399,348, 2,796,096 and 4,141,775.
While many of the prior art machines can be successfully used to produce curved wood members, much of the prior art equipment is prohibitively expensive, difficult to use or difficult to adapt rapidly to production of different sizes of curved members.
Despite the deficiencies of the prior art equipment and techniques available for fabricating "half-round top" window and door frames by glue lamination of thin wood layers, the demand for such windows, doors and other architectural structures having similar curves has expanded enormously with the growth in the popularity of post-modern architecture.
Consequently, there is a substantial need for a curve-forming laminating fixture which is sturdy, well-suited for use in high volume production, utilizes a minimum amount of shop floor space, and of substantial importance, which can accommodate a variety of frame sizes economically and easily.